Resource Centre - Definitions, concepts & processes of the eye

Definitions, concepts & processes of the eye

Accommodation
Accommodation is the ability of the eye to alter the shape of the lens so that the eye can focus on objects from a range of distances.

Anterior Chamber
The anterior chamber is part of the eye, which is fluid-filled and found behind the cornea and in front of the iris.

Posterior Chamber
The posterior chamber is the part of the eye, which is in the space behind the iris and in front of the lens.

Blind Spot
The blind spot is small area of the retina where there are no photoreceptors. Therefore, a portion of our range of vision is not registered. However, due to information from the other eye and the surrounding image, the brain can create a complete picture.

Brain
The brain is an organ found inside the skull and is part of the central nervous system. It is responsible for muscle control, coordination, interpreting and distributing information and controls and regulates most bodily activities.

Central Nervous System
The central nervous system consists of the brain and the spinal cord. The CNS receives signals from the rest of the body via neurons and controls the body's response.

Central Vision
Central vision is the area of vision that results from the fovea and macula. It is used for fine detail and colour.

Eyelash
An eyelash is one of the short hairs, which grows from the edge of an eyelid. Its function is to protect the eye by collecting and removing dust and foreign particles from the eye.

Eyelid
The eyelid is one of two thin layers of skin, which cover and protect the eye. It is connected to a row of eyelashes.

Eye Socket
The eye socket is the cavity in the skull, which holds the eye and serves to protect the eye from danger.

Focal Point
The focal point is the point on the retina where light rays converge and a sharp image of the object is formed.

Focus
When an image is focused, it appears sharp and well defined. It is the point at which light rays refracted from the lens converge on the retina to form a clear image.

Lacrimal Gland
The lacrimal gland is the gland responsible for producing tears and is located in the outer, upper part of each eye socket.

Peripheral Vision
Peripheral vision is the area of vision, which is not the central focus and occurs at the outer part of the field of view. Peripheral vision uses rod photoreceptor cells.

Photoreceptors
Photoreceptors are light sensitive cells and are found in the retina. They can be in the form of rod cells or cone cells.

Rod cells respond to low levels of light but are not useful for fine detail and cannot distinguish colour. They are found at the outer edges of the retina but are not present in the fovea. Rod cells are used in peripheral vision.

Cone cells are sensitive to colour and high light levels. They are found particularly in the macula, and therefore the fovea. Cone cells are used for fine detail and for central vision.

Refraction
Refraction is the process by which light rays are bent as they travel through the lens. This occurs because the light rays move into a different medium, when entering the lens, and this causes the speed of the light waves to slow down, altering the direction of the light.

Sensory Neurons
Sensory neurons are nerve cells, which are used, in the context of the eye, to carry sensory information from the retina, through the optic nerve, to the brain.

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